In recent years there has been significant progress in the development of pressure-compensated directional control valve assemblies for fluid control systems. U.S. Pat. No. 3,693,506 discloses a control circuit for a plurality of manual control valves, each controlling a fluid motor. The control circuit includes a logic system for sensing each load-actuating pressure, and for selecting the highest pressure sensed and directing this pressure to actuate means for controlling a source of supply pressure. U.S. Pat. No. 3,592,216 discloses a flow control valve for use with such a control circuit. The flow control valve limits the pressure supplied to the manual control valves and maintains the required fluid flow thereto. U.S. Pat. No. 3,631,890 discloses a flow-extending bypass valve which may be used with the control circuit. The flow-extending bypass valve adjusts automatically to bypass fluid at an increased differential pressure when a fluid motor is actuated, thereby extending the flow capacity of the manual control valve associated with the fluid motor. U.S. Pat. No. 4,145,958 discloses that such a pressure-compensated directional control valve assembly may incorporate a manual control valve having a float position as well as neutral and power positions.
There remains a need in the art for a fluid control system wherein each control section includes its own individually variable flow control mechanism independently responsive to section load pressure and capable of controlling the flow rate delivered to that section while the manual control valve spool is in a full power position. When a directional control valve assembly incorporates a plurality of flow control sections, or when a plurality of assemblies are incorporated in the fluid control system, each flow control mechanism should be individually variable and independently responsive to the load pressure of its section.